/**
 *	3.三条边都相等的三角形叫等边三角形，有两条边相等的三角形的等腰三角形，三条边都不相等叫做不等边三角形，
 *	写一个程序提示输入三角形的三条变长，程序需要判断这些数字代表的是什么三角形，提示：什么是程序另外要检查的？
**/

#include <stdio.h>

int main(void)
{
	float a, b, c;
	printf("please input the triangle's three side length: ");
	scanf("%f %f %f", &a, &b, &c);

	if(a <= 0 || b <= 0 || c <= 0)
	{
		printf("the length of triangle side is not positive!\n");
		return 1;
	}

	if(a + b <= c || a + c <= b || b + c <= a)
	{
		printf("whatever two side must be less than other side\n");
		return 1;
	}	
	
	if(a == b && b == c)
		printf("equilateral\n");
	else if (a == b || a == c || b == c)
		printf("isosceles\n");
	else
		printf("scalena\n");

	return 0;
}
